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A higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults. The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents.
Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 RESEARCH ARTICLE Open Access Improved insulin sensitivity and body composition, irrespective of macronutrient intake, after a 12 month intervention in adolescents with pre-diabetes; RESIST a randomised control trial Sarah P Garnett1,2,3*, Megan Gow1,3, Mandy Ho3, Louise A Baur2,3, Manny Noakes4, Helen J Woodhead5,6, Carolyn R Broderick7,8, Kerryn Chisholm9, Julie Briody10, Sukanya De2, Katherine Steinbeck11, Shubha Srinivasan1, Geoffrey R Ambler1,3 and Chris T Cowell1,2,3 Abstract Background: A higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents We hypothesised that a moderate-carbohydrate (40-45% of energy), increased-protein (25-30%) diet would be more effective than a high-carbohydrate diet (55-60%), moderate-protein (15%) diet in improving outcomes in obese, insulin resistant adolescents Methods: Obese 10–17 year olds with either pre-diabetes and/or clinical features of insulin resistance were recruited at two hospitals in Sydney, Australia At baseline adolescents were prescribed metformin and randomised to one of two energy restricted diets The intervention included regular contact with the dietician and a supervised physical activity program Outcomes included insulin sensitivity index measured by an oral glucose tolerance test and body composition measured by dual-energy x-ray absorptiometry at 12 months Results: Of the 111 adolescents recruited, 85 (77%) completed the intervention BMI expressed as a percentage of the 95th percentile decreased by 6.8% [95% CI: −8.8 to −4.9], ISI increased by 0.2 [95% CI: 0.06 to 0.39] and percent body fat decreased by 2.4% [95% CI: −3.4 to −1.3] There were no significant differences in outcomes between diet groups at any time Conclusion: When treated with metformin and an exercise program, a structured, reduced energy diet, which is either high-carbohydrate or moderate-carbohydrate with increased-protein, can achieve clinically significant improvements in obese adolescents at risk of type diabetes Trial registration: Australian New Zealand Clinical Trail Registry ACTRN12608000416392 Registered 25 August 2008 Keywords: Insulin sensitivity, Body composition, Macronutrient intake, Adolescents, Pre-diabetes * Correspondence: sarah.garnett@health.nsw.gov.au Institute of Endocrinology and Diabetes, The Children’s Hospital at Westmead, Locked Bag 4001, Westmead, Sydney, NSW 2145, Australia Kids Research Institute, The Children’s Hospital at Westmead, Locked Bag 4001, Westmead, Sydney, NSW 2145, Australia Full list of author information is available at the end of the article © 2014 Garnett et al.; licensee BioMed Central Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Background There is substantial interest in the effect of the macronutrient composition of the diet on potentiating weight loss and improving cardiometabolic risk [1,2] Results from several studies indicate that a weight loss diet with increased protein and reduced carbohydrate may increase body fat mass loss, attenuate loss of fat free mass (FFM) and improve lipid profile and glucose homeostasis, compared with a conventional high carbohydrate, low fat diet [3] It is speculated that protein is superior to carbohydrate in promoting satiety as well as dietary induced thermogenesis, with no unfavourable health implications [4,5] In addition, high carbohydrate diets may lead to higher post prandial glucose and insulin spikes, placing increased demands on beta cell function and exacerbating insulin sensitivity [6] However, improved outcomes with an increased protein diet are not consistently reported A recent systematic review [7] identified three randomised control trials (RCT), conducted in highly controlled environments, two were in residential camps [8,9] and the other in a boarding school [10], comparing increased protein to isoenergetic standard protein diets in obese children; none reported differences in weight loss, cardiometabolic risk, or glycaemic status between diets However, there is a paucity of trials in free-living overweight or obese adolescents We undertook an RCT, known as Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers (RESIST), with the aim of determining the effectiveness of a moderate-carbohydrate, increased protein diet compared to a high carbohydrate diet on insulin sensitivity in adolescents with pre-diabetes and/or clinical features of insulin resistance treated with metformin We hypothesised that the moderate-carbohydrate, increasedprotein diet would be more effective than the highcarbohydrate diet in improving insulin sensitivity, body composition and metabolic profile The six month results have been previous published and in contrast to our hypothesis, demonstrated no significant differences in weight loss or metabolic profile between dietary groups [11] The aims of this manuscript are to describe the changes in whole body insulin sensitivity index (ISI), derived from an oral glucose tolerance test (OGTT), and in body composition, measured by dual-energy x-ray absorptiometry (DXA), after 12 months of intervention Methods This study was a 12 month parallel RCT which took place at The Children’s Hospital at Westmead (CHW) and Campbelltown Hospital, Sydney, Australia This study was conducted according to the guidelines laid down in the Declaration of Helsinki and was approved by CHW Human Research Ethics Committee (07/CHW/12) and Sydney South West Area Health, Western Zone (08/ Page of 10 LPOOL/195) Written informed consent from parents and assent from the adolescents was sought prior to enrolment The protocol for the study has been published [12] All participants were treated with metformin and received the same 12 month lifestyle intervention The only difference between treatment arms was the macronutrient composition of the diet The intervention consisted of three phases: I (0–3 months): Intensive dietary intervention II (4–6 months): Intensive exercise program plus dietary support III (7–12 months): Participants were encouraged to continue with their diet/exercise regimens and metformin Study population Participants were recruited through physician referral [12] After a patient was assessed and identified as meeting the trial criteria, the patient and parent/carer made contact with study dieticians who explained the study, sent information sheets/consent forms and booked appointments Treatment allocation (allocation ratio 1:1) occurred centrally by minimisation [13], stratified by sex, pubertal stage and BMI status [14], with the aid of computer software [15] at CHW, by study dieticians Inclusion criteria Ten to 17 year old adolescents who were overweight or obese, as defined by the International Obesity TaskForce [14] with either pre type diabetes [16] and/or clinical features of insulin resistance As previously described clinical features of insulin resistance were defined as a fasting insulin (pmol/L)/glucose (mmol/L) ratio >20 with one or more of the following: acanthosis nigricans, polycystic ovarian syndrome, hypertension, fasting HDL cholesterol 120 kg Our target sample size was 108 (54 in each arm) This was based on the primary outcome, change in whole body ISI of 0.8 (SD 1.3), with an 80% chance of detecting a significant increase in ISI at the two sided 5% level and included a 20% dropout rate [12] A total of 111 entered the study between January 2009 and November 2011, Figure Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Page of 10 Referred (n= 188) Declined to participate (n=43) Assessed for eligibility (n=145) Excluded (n=31) Did not meet inclusion criteria (n=31) Declined to participate (n=3) Allocated (n=111) Allocated to a moderate carbohydrate, increased protein diet (n=56) Phase I: Intensive dietary intervention Followed up (n=55) Withdrawals (n=1) Phase II: Intensive exercise intervention Followed up (n=49) Unable to attend month follow-up (n=2) Withdrawals (n=4) Phase III: Maintenance Followed up (n=39) Withdrawals (n=10) Allocated to a high carbohydrate, low fat diet (n=55) Phase I: Intensive dietary intervention Followed up (n=51) Withdrawals (n=4) Unrelated medical issues (n=1) Did not want to participate (n=3) Phase II: Intensive exercise intervention Followed up (n=49) Withdrawals (n=2) Did not want not to participate (n=2) Phase III: Maintenance Followed up (n=46) Withdrawals (n=5) Did not want not to participate (n=5) Not contactable Figure RESIST participant flow Interventions Metformin Consistent with clinical practice at CHW all participants were treated with metformin (Diabex) which was provided at no cost for the duration of the study The initial dose was 250 mg twice daily After weeks this was increased to a final dose of 500 mg twice daily Diet Diet was a high-carbohydrate diet, with 55-60% of total energy as carbohydrate (moderate glycaemic load), 30% fat (≤10% saturated fat) and 15% protein Diet was a moderate-carbohydrate, increased-protein diet, with 40-45% of total energy as carbohydrate (moderate glycaemic load), 30% fat (≤10% saturated fat), 25-30% protein Diets were prescriptive at two different energy levels: 6,000 to 7,000 kJ (10 to 14 years) or 7,000 to 8,000 kJ (15 to 17 years) The energy levels were a range for each age group, to enable prescribed energy to individualize, depending upon the energy requirements Details of the delivery of the intervention have been previously described [12] Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Exercise Phase I Standardised physical activity advice, consistent with recommendations for adolescents [17] was delivered by study dieticians Phase II Participants received, free of charge, a supervised exercise program, 45–60 minutes, twice/week for 12 weeks in a commercial gym, including Fitness First, or a local park in the geographic area in which they lived The program was designed to be of moderate-tovigorous intensity and consisted of circuit training with an age-appropriate mix of resistance and aerobic stations, conducted by qualified fitness trainers, blinded to treatment arm Participants were also encouraged to exercise at least once a week at home Medical care Clinical progress was reviewed by the participant’s primary or study physician, who was blinded to the trial arm of the adolescent and who assessed puberty using Tanner Staging [18], blood pressure, acanthosis nigricans [19] and menstrual history Page of 10 overnight fast [12] Blood drawn was analysed using standard techniques for lipids, alanine aminotransferase (ALT), gamma-glutamyl transferase (GTT)), and renal function tests (urea, electrolytes, and creatinine) Abnormal triglycerides and HDL-cholesterol were defined as ≥1.7 mmol/L and 96% of the adolescents had a BMI >97th centile which is beyond the scope of the CDC2000 reference data [24] Blood pressure was measured using an automated blood pressure monitor (Dinamap 1846SX) Elevated blood pressure was defined as ≥90th centile [25] An OGTT was performed after an Statistical analysis Data were analysed using PASW statistical software for Windows, version 18 (SPSS Inc) Differences between continuous data were examined using independent sample t-tests for normally distributed data or Mann–Whitney tests for non-parametric data Chi-squared tests were used to examine differences in categorical data; odds ratios were used to examine the magnitude of the association Correlations between variables were assessed by Pearson’s Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Page of 10 correlation coefficients or Spearman’s rho for normally distributed and non-parametric data, respectively Consistent with an intent-to-treat approach, all available data for participants as originally randomly assigned, were retained Linear mixed models with an unstructured covariance were used to test for the effects of diet and time (baseline, three, six and 12 months) Non-parametric data were log transformed Age at baseline and age difference between visits were tested in the modelling but were not statistically and/or clinically significant and hence results have been expressed as unadjusted models The least significant difference method was used for post-hoc comparisons The assumptions of modelling were tested and met Mean changes and differences derived from linear mixed models are presented with 95% CIs Data that were log transformed are presented as geometric means with 95% CIs Results Of the 111 adolescents (66 girls) recruited, 85 (77%) completed the 12 month intervention (Figure 1) There was no statistical difference in baseline anthropometry, body composition or clinical parameters between groups (Table 1) The exception was that more participants had pre-diabetes in the moderate-carbohydrate, increased-protein group (n = 11; 19.6%) compared to the high-carbohydrate group (n = 3; 5.5%), P = 0.024 There was also no statistical difference in baseline anthropometry, body composition or clinical parameters between the completers and the drop-outs Participants who dropped out were more likely to come from a single parent family (odds ratio 4.3 [95% CI: 1.6 to 12.0], P = 0.05) Attrition rate was not statistically significantly different between diet groups (Figure 1) Over the 12 month intervention there was a statistically significant (P < 0.001) decrease in height z-score from 1.27 at baseline to 0.76 at 12 months and the number of children who were pre-pubertal (Tanner stage and 2) decreased from 30.9% to 15.1% The change in height and pubertal stage was not significantly different between diet groups Table Baseline characteristics Intervention group Moderate-carbohydrate, increased-protein diet (n = 56) High-carbohydrate, low-fat diet (n = 55) P* Age and sex Age years median [range] 13.0 [10.1 to 16.5] 13.2 [10.2 to 17.4] 0.959 Girls n (%) 34 (60.7) 32 (58.2) 0.786† Tanner stage (12.7) (12.7) (16.4) 11 (20.0) 15 (27.3) (16.4) 15 (27.3) 16 (29.1) (16.4) 12 (21.8) Pubertal status‡ n (%) Anthropometry Mean (SD) unless otherwise indicated Weight kg 90.7 (19.0) 90.7 (21.2) 0.992 Height z-score 1.27 (1.29) 1.30 (1.11) 0.894 Weight z-score 2.73 (0.53) 2.68 (0.57) 0.646 BMI z-score 2.39 (0.25) 2.33 (0.32) 0.253 BMI %95 centile 133 (19) 132 (23) 0.770 Obese§ n (%) 55 (98.2) 52 (94.5) 0.300† 43.5 (10.0) 42.6 (11.7) 0.683 Body composition (DXA)| Total body fat (kg) Total fat % 49.5 (5.5) 48.3 (5.7) 0.249 Total fat free mass (kg) 44.4 (11.3) 45.1 (11.4) 0.740 Fat free mass index 1.66 (0.24) 1.69 (0.29) 0.638 *P independent sample t-tests unless otherwise indicated † Chi-squared test ‡ One girl in the moderate carbohydrate, increase protein diet group had missing data § Obesity defined by International Obesity Taskforce [14] | DXA: Dual-energy x-ray absorptiometry Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Effects of intervention on insulin sensitivity index ISI increased between baseline and three months, which remained significantly different from baseline at 12 months; estimated mean difference 0.23 [0.06 to 0.39], P = 0.009; Figure 2a The magnitude of change was similar for girls and boys, although boys commenced the trial with a lower median ISI (1.2 [range 0.3 to 3.0]) compared to girls (1.4 [0.3 to 3.4]), P = 0.04 Adjusting for puberty and/or age did not alter the outcome There was no significant difference in ISI between diet groups at any time point Effects of intervention on total body fat Total body fat% decreased over the 12 month intervention (P < 0.001, Figure 2b) There was a significant sex and pubertal interaction in the modelling After adjusting for pubertal stage, the magnitude of change was similar for boys and girls, however, boys commenced the Page of 10 trial with a lower total body fat percentage (46.3% ± 5.3) compared to girls (50.7% ±5 3), P < 0.001 There was no significant difference in total body fat% between diet groups at any time point Similarly the FMI significantly (P = 0.009) decreased from 16.2 ± 0.4 (estimated marginal mean ± SE) at baseline to 15.6 ± 0.5 at 12 months and there was no significant difference (P = 0.421) in FMI between diet groups at any time point Effects of intervention on fat free mass index After three months of intervention there was a significant decrease in FFMI, followed by a significant increase between three and 12 months (Figure 2c) Analysis stratified by sex indicated that girls, but not boys, had a significant decrease; estimated mean difference (0.03 [95% CI: 0.01 to 0.05], P = 0.005) in the FFMI during the first three months, which increased (0.03 [0.001 to 0.06], P = 0.014) to baseline levels at 12 month Boys’ FFMI did Figure Glycemic status and body composition measures by dietary group over the 12 month intervention Estimated marginal means (SE) are presented from linear mixed models for the moderate-carbohydrate, increased-protein diet group (▼) and the high-carbohydrate diet group (△) a: Insulin sensitivity index 1Significance between baseline and months and 12 months as indicated 2Significance between and 12 months b: Total body fat percent measured by dual energy x-ray absorptiometry (Fat % DXA) 1Significance between baseline and months and 12 months as indicated 2Significance between and 12 months c: Fat free mass index 1Significance between baseline and months and 12 months as indicated 2Significance between and 12 months d: BMI%95th centile 1Significance between baseline and months, months and 12 months as indicated 3Significance between and months 4Significance between and 12 months Garnett et al BMC Pediatrics 2014, 14:289 http://www.biomedcentral.com/1471-2431/14/289 Page of 10 not change over the first three months, but FFMI was higher at 12 months compared to both baseline (0.09 [0.06 to 0.12], P < 0.001]) and three months (0.11 [0.06 to 0.15], P < 0.001) Adjusting for puberty and/or age did not alter the outcome There was no significant difference between diet groups at any time point Effects of intervention on BMI%95th centile BMI%95th centile decreased between baseline and 12 months (P < 0.001, Figure 2d) The decrease in BMI% 95th centile occurred between baseline and six months and there was no significant change over the following six months The magnitude of change (estimated mean difference 6.8% [95% CI: 4.9 to 8.8]) over the 12 months was similar for boys and girls, although boys commenced the trial with a higher mean (±SD) BMI%95th centile compared to girls; 136.8 ± 21.1 and 129.3 ± 20.6, P = 0.020, respectively There was no significant difference between diet groups at any time point Effects of intervention on lipids and blood pressure Between baseline and 12 months there was a significant increase in HDL-cholesterol and a significant decrease in diastolic blood pressure (Table 2) There were no significant differences between baseline and 12 month measures of LDL-cholesterol , triglycerides or systolic blood pressure, nor was there any significant difference in lipids or blood pressure between diet groups at any time point Sex was not a significant predictor of change in HDL-cholesterol, LDL-cholesterol or triglycerides However, a sex difference in blood pressure was observed The magnitude of change in both SBP z-score and DBP z-score over the 12 months was similar for boys and girls, although boys commenced the trial with a higher blood pressure At baseline the SBP z-score (estimated marginal mean (SE)) for boys and girls was 1.10 (0.14) and 0.49 (0.16), respectively and DBP was 1.13 (0.09) and 0.75 (0.11), respectively Dietary adherence The geometric mean [95% CI] for the reported energy intake over the 12 month intervention was 5.97 [5.94 to 6.37] MJ per day for adolescents randomised to the moderate-carbohydrate, increased-protein diet and 6.41 [6.00 to 6.85] MJ per day for adolescents randomised to the high-carbohydrate diet The difference was not significant (P = 0.126), nor did the reported energy intake differ over time (P = 0.935) Protein % energy was significantly (P = 0.027) higher in the moderate-carbohydrate increasedprotein group compared to the high-carbohydrate group, 20.3% [19.3 to 21.2] and 18.8% [17.8 to 19.2], respectively, and this did not differ over time (P = 0.081) There was no statistical difference in reported fat % energy (both groups 30.4% [28.5 to 32.2], P = 0.710) or carbohydrate % energy (46.5% [44.7 to 48.1] for the increased-protein group and 48.2% [46.4 to 49.9] for the high-carbohydrate group, P = 0.155) Fat % energy intake did not change significantly over time (P = 0.191) In contrast, reported carbohydrate % energy was significantly higher in both groups at six months compared to six weeks, three months and 12 months, P = 0.003 Clinical outcomes in adolescents who completed the intervention There was no statistical difference in clinical outcomes between diet groups at any time point; data has been pooled for this analysis, Table BMI %95th centile Of the 85(82 obese at baseline) who completed the study, 67 (78.8%) decreased BMI %95th centile and 18 increased BMI %95th centile Two participants completed the 12 month intervention with a weight within the normal range, and 12 were classified as overweight Baseline sex, age, puberty, weight, or fasting insulin were not significantly associated with change in BMI %95th centile However, participants who entered the trial with a higher ISI, lost less weight (BMI %95th centile), rho −0.26, P = 0.018 Pre-diabetes Eighty-three participants had glycaemic status measured at baseline and 12 months Eight (9.6%) of the 83 participants had pre-diabetes at baseline (three impaired fasting glucose (IFG), four impaired glucose tolerance (IGT), one with both IFG and IGT), but only had pre-diabetes at 12 months The six participants who improved glycaemic Table Lipids and blood pressure at baseline and 12 months After 12 months intervention P* Triglycerides mmol/L† Baseline 1.1 [1.0-1.2] 1.0 [0.9-1.1] 0.209 HDL-C mmol/L 1.05 (0.02) 1.12 (0.03)